Well, this article claims that Kilpatrick's raid was EXPRESSLY for that purpose, and gives some good reasons and backs it up. I will try to dig up the issue # etc.
The official purpose of Dahlgren's raid was to free prisoners from Libby Prison, period. None of Dahlgren's superiors or any of his staff were aware of any plan or issued any orders to burn Richmond and kill Davis and his cabinet. Some sort of proclamation stating that goal was supposed to have been found on Dahlgren's body, allegedly in his false leg, but even then there was nothing that indicated that the Union Army command authorized such actions, much less that Abraham Lincoln personally ordered it. There is nothing in the OR to indicate that the assassination of Davis, or even his capture was ordered. Yet you have no problem stating with perfect certainty that Lincoln ordered the murder of Jefferson Davis, so that somehow makes Booth's actions acceptable.